In this field, the solutions in use comprise filling the moulds with a reference liquid (for example water), after having weighed the reference liquid (in a greater amount) and then weighing the liquid remaining and, by difference, obtaining the volume of liquid contained in the mould.
However, this approach has several problems.
Firstly, this method is not very precise because the density of the reference liquid is not known exactly.
The moulds have air vent holes which must be sealed and the joints between the mould pieces must also be sealed to prevent escape of the liquid, and this operation is not easy.
Moreover, the need to wet the mould prevents easily measuring the capacity of all the moulds produced.
Patent document US2004/017563 discloses a system for measuring various features of an object, including the volume of the object itself.
U.S. Pat. No. 6,407,818B1 discloses a system for measuring the shape of an object in transit on a belt for being cut.
However, these patent documents do not deal in particular with the problem of how to accurately measure the volume inside a mould having an inner surface with a double curvature, which is typical of a mould used for a container (for example, a glass bottle).